Inorganic polyphosphate (poly P) occurs ubiquitously in all living cells and regulates many molecular and biological processes. Nevertheless, poly P is scarcely studied and little is known about poly P metabolism and its exact molecular functions; especially in eukaryotes. In our group we have developed methods to quantify poly P, to stain and localize poly P and to screen for poly P binding proteins. We are using these tools to investigate poly P metabolism and functions in fungi, plants and algae. However, at the moment our main efforts are devoted to the study of poly P metabolism in the yeast Saccharomyces cerevisiae and of poly P in fungal cell walls.
Poly P in Saccharomyces cerevisiae:
We have developed a fast and easy method for the quantification of poly P in yeast, which is amenable for large-scale analyses. This allowed extraction and quantification of poly P in mutant strains of all non-essential yeast genes. From this screen we conclude that at least 5% of all yeast genes are required for the maintenance of normal poly P levels. We are now studying specific pathways to determine their link with poly P metabolism. In addition, we study phenotypical differences in poly P hypo- and hyper-accumulating strains in order to learn more about the biological significance of poly P accumulation in yeast.
Cell wall localized poly P:
One of our major goals and a very difficult problem is the specific localization of poly P. We have developed a staining method that is based on poly P binding proteins and immunohistochemical detection that allows for highly sensitive localization of poly P in fungal cell walls. We have used this technique for a systematic study of poly P in fungi from all fungal phyla. In the future we will also define procedures to stain poly P intracellularly.